Trying to set up my son’s series s- on his birthday! Stuck on ‘update complete!’ Screen...

Greetings- frustrated dad here trying to set up my son’s series s on his birthday! He started setting it up before school and I think did some things out of order. Performed update then had to go to school and I think his younger brother put console to ‘sleep’ all day. Came home and can’t get past the update complete screen. It is literally a brick wall. He tries to finish set up in the app and it asks for letter code then asks for QR code to be scanned then just keeps saying error every time. Have tried shut down, unplug, turn off router, hard reset, uninstalling app, trying different phone etc. have also tried to factory reset but troubleshooting screen won’t stay up for longer than 1 second so incredibly frustrated! Online support was clearly an AI bot and was useless. Any help gratefully received.

:)